DevSecOps workflows with conditional CI/CD pipeline rules

This post introduces and explains the `rules` feature in GitLab CI/CD, detailing its various keywords (`if`, `changes`, `exists`, `allow_failure`, `variables`, `when`, `needs`) and their practical use cases. It also covers `workflow:rules` for controlling entire pipeline behavior. The post provides code examples for conditional job execution based on branch names, file changes, and variable values, and discusses how these rules can improve developer experience and security/quality assurance workflows.